Fingerprint sensing and matching is a commonly used technique for personal identification or verification. For example, one approach to fingerprint identification involves scanning a sample fingerprint or an image with a biometric reader/sensor and storing the image and/or unique characteristics of the fingerprint image. The characteristics of a sample fingerprint may then be compared to information for reference fingerprints already in a database to determine proper identification of a person, such as for verification purposes.
Biometric sensors, particularly fingerprint biometric sensors, are generally prone to being defeated by various forms of spoof samples. In the case of fingerprint readers, a variety of techniques are known for presenting readers with a fingerprint pattern of an authorized user that is embedded in some kind of inanimate material such as paper, gelatin, epoxy, latex, or the like. Thus, even if a fingerprint reader can be considered to reliably determine the presence or absence of a matching fingerprint pattern, it is also critical to the overall system security to ensure that the matching pattern is being acquired from a genuine, living finger, which may be difficult to ascertain with many common sensors.
There are various conventional solutions available in distinguish spoof samples from a live finger. One approach is described in U.S. Pat. No. 7,433,729 B2, where a technique of spoof detection is disclosed using infrared sensors. Another approach is described in PCT1US2015/017557, where a technique of spoof detection is disclosed using optical wavelengths to capture characteristics of skin samples being analyzed. As ultrasonic sensors have become increasingly popular in mobile devices, it is desirable to have apparatuses and methods for liveness and spoof detection with ultrasonic fingerprint sensors.